This invention relates to the construction and operation of superconducting rotating machines, and more particularly to superconductor winding construction for use in superconducting motors.
Superconducting air core, synchronous electric machines have been under development since the early 1960s. The use of superconducting windings in these machines has resulted in a significant increase in the magneto motive forces generated by the windings and increased flux densities in the machines. However, superconducting windings generate tremendous internal stresses that attempt to force the superconducting windings into circular shapes. Certain applications require the superconducting windings to be non-circular for various reasons and the internal stresses must be alleviated or supported.
The invention features an internally supported superconducting coil assembly. The invention includes several superconducting windings and at least one internal coil support member that forms a laminate stack alternating between an internal support member and a superconducting winding. Embodiments of this aspect of the invention may include one or more of the following features.
The internal coil support members are especially advantageous when non-circular superconducting windings are utilized. In certain embodiments, a racetrack shaped superconducting winding is used. The racetrack shape is defined by two opposing arcuate end sections and two substantially straight side sections. The internal magnetic stresses generated by the superconducting winding attempts to force the superconducting winding to become round in shape. The internal coil support members help alleviate the internal stresses. The internal coil support members work better than external support members because the bending stresses are greatest near the center of the winding, away from any external supports.
In certain embodiments, the superconducting coil assembly laminate can be fixed to a rotor body for use in a rotating machine by passing a bolt through the laminate and into the rotor body. The bolt, or multiple bolts, will help unify the laminate into a unitary whole. The laminate may also be impregnated with epoxy to achieve a unitary whole.
The internal coil support members must have openings to allow electrical connection between adjacent superconducting windings that are separated by the internal coil support member. The internal coil support member is usually made of stainless steel, which further helps quench the magnetic forces.